Consider the following statements: 1. In a seismograph, P waves are recorded earlier than S waves. 2. In P waves, the individual particles vibrate to and fro in the direction of wave propagation whereas in S waves, the particles vibrate up and down at right angles to the direction of wave propagation. Which of the statements given above is/are correct?
- A. (a) 1 only
- B. (b) 2 only
- C. (c) Both 1 and 2
- D. (d) Neither 1 nor 2
Answer: C
Explanation
Statement 1 is correct. P-waves (Primary waves) are compressional waves that travel faster through the Earth’s interior than S-waves (Secondary waves). Consequently, they are the first to be recorded by a seismograph. Statement 2 is also correct. P-waves are longitudinal waves, meaning particles vibrate back and forth (to and fro) parallel to the direction of wave propagation, causing compression and rarefaction. S-waves are transverse waves, meaning particles vibrate perpendicular (up and down or side to side) to the direction of wave propagation. Both statements accurately describe the characteristics of seismic waves. This question tests fundamental concepts in geomorphology, a key area in UPSC Geography.